Washington Redskins running back Clinton Portis' Nov. 29 concussion in a game against the Atlanta Falcons illustrates the danger of collisions on the field -- and it may be cases like his that have changed the way pro football views these injuries.
Portis was hurt in a helmet-to-helmet hit in the first quarter of the game.
"We kept Clinton at home just to get rest," Redskins coach Jim Zorn told the Associated Press. "That was kind of doctor's orders."
The incident comes just days before the National Football League tightened rules regarding when players can return to action after suffering a concussion.
Effective immediately, the new policy, issued by NFL commissioner Roger Goodell, expands the list of symptoms that would preclude a player from returning to a game or practice on the same day.
The symptoms include:
Being unable to remember assignments or plays or other signs of confusion
Gap in memory
Abnormal neurological examination, including abnormal pupillary response, persistent dizziness or vertigo, and abnormal balance on sideline testing
New and persistent headache, especially if accompanied by sensitivity to light, nausea, and vomiting
Loss of consciousness
A policy instituted in 2007 prohibited players from returning to a game or practice if they lost consciousness after suffering a concussion.
"This new return-to-play statement reinforces our commitment to advancing player safety," Goodell said in a memo to the 32 NFL teams. "Along with improved equipment, better education, and rules changes designed to reduce impacts to the head, it will make our game safer for the men who play it and set an important example for players at all levels of play."
Dr. Wendy Wright, a neurologist at Emory University in Atlanta, said she was pleased to see that the policy was more conservative than she expected.
However, she said in an interview, "it remains to be seen if the conservative measures are too conservative or not conservative enough, and that's the kind of thing that has to play out long term."
She acknowledged that one has to be careful when a player's career is at stake, "but when you're talking about protecting the brain from long-term consequences of injury, as a neurologist, of course, I think you can't be too careful."
The new rules were developed by the league's medical committee on concussions in consultation with team doctors, outside medical experts, and the NFL Players Association.
The issue of concussions in the NFL has garnered more attention in recent months and was the subject of a congressional hearing in October.
Last month, Goodell informed teams that he was considering changing the concussion policy.
Currently, several high-profile players are recovering from concussions, including the quarterbacks in last year's Super Bowl, Ben Roethlisberger of the Pittsburgh Steelers and Kurt Warner of the Arizona Cardinals, and star running back Brian Westbrook of the Philadelphia Eagles.
The new policy also establishes rules for when a player can return to game action after being removed for the duration of a practice or game.
"The player should not be considered for return-to-football activities until he is fully asymptomatic, both at rest and after exertion, has a normal neurological examination, normal neuropsychological testing, and has been cleared to return by both his team physician(s) and the independent neurological consultant," the policy states.
All teams have selected an independent neurologist and they have been approved by the league.
Dr. Kenneth Perrine, a neuropsychologist at Hackensack University Medical Center in Hackensack, N.J., told MedPage Today that he thought the new policy would have a positive effect around the league.
"I think it's going to encourage the players to go through the process," said Perrine, who is the consulting neuropsychologist for the NFL's N.Y. Jets and the National Hockey League's N.Y. Islanders.
But, he added, "we've been pretty cautious anyway." According to Perrine, many of the newly mandated rules are already in place, at least in his experience.
The only aspect of the policy that is actually new, he said, is the requirement for teams to have an independent neurologist.
In the memo announcing the policy, Goodell urged players to be forthcoming about their condition.
A survey conducted by the Associated Press last month found that 30 of 160 NFL players had hidden or downplayed the effects of a concussion at some point during their careers, likely because of both a fear of letting down their team and a culture in which players are expected to play through pain.
But Perrine said players have become more aware of the seriousness of concussions in recent years and have become more candid about feeling ill effects.
"They realize that this is their profession, this is their game, but it's also their lives, and they want to make sure that they're not going to do something that's going to have a negative impact down the line," he said.
Wright said only time will tell whether the new policy does enough to protect players' health.
"The only way to tell if it goes far enough is to track the health of the players over the coming years and to make sure that there's a demonstrable improvement in their health long term, that we're not seeing the types of memory problems, the types of health problems that we've seen in the past," she said.
Associated Press reports contributed to this report.